The "let the kids sleep"

F

fontoponto

Well-known member
Hi guys,
I play my bass in the living room with a EBS Preamp/Headphone Microbass and I wanted something similar for the Guitar. Just using what I have is not DIY :-)
It's a box with a
  • - Baja Reactor
  • - Omnicab
  • - Stereo Headphone amp with Aux-In and an additional mono out to drive a cab in case it has to be loud in the room
The combination is pretty cool. I copied the headphone amp from here https://web.archive.org/web/2024052.../musical-instrument-stereo-headphone-amp.html
The original site was up until shortly after I finished the pcb.

Well so far so good but in the end it is a FAILURE.

It hurts me...
The reactor is oscillating like hell in various settings because my layout is :poop: :poop: :poop: :poop: :poop: :poop: :poop: :poop:
Why am I always trying to fit stuff into really small enclosures?
The headphone and aux jacks are so fiddly, no space was left above the pot and below the lid of the box so they just fit in perfectly but the holes are crooked so no rough treatment is allowed. It's so hilarious... I lost the nuts of the switches and in the end I had no desire to break my fingers by trying to get the leds in place. Maybe I will salvage it... Maybe it has to be a reminder to not solder up everything at once when you are not sure that your layout is ok.
The "Marriage Keeper" encouraged me to box it up completely but... It' sad.
The next step is a larger box with a 60W amp and a larger pcb with a better layout for the reactor (just like Baja did it).

IMG_5939.JPG IMG_5938.JPG
 
I'll echo Erik. Props on the execution.
I'll also note, a lot of Baja designs seem to be extremely finicky/half way work with oscillation being a common issue. Not saying that's he case with this circuit, no idea. If you haven't already, I'd poke around FSB and the like and make sure there are more fully functioning builds documented than not.

I have always been curious about building up an amp with one of the dedicated headphone amp ICs. Like this one for $2 from EG
theelectronicgoldmine.com

G27000 ~ Toshiba TA8119P Stereo Headphone Amplifier IC

Toshiba stereo headphone amplifier IC Part# TA8119P in the 16 pin feed-thru dip package by Toshiba requires very few external components. Original Toshiba Part - New!
theelectronicgoldmine.com theelectronicgoldmine.com

Toshiba TA8119P datasheet

Or the NJM2777which requires very little external circuitry and runs happily at 9v
1000006349.png
 
Thank you guys!

jwin615 said:
I'll also note, a lot of Baja designs seem to be extremely finicky/half way work with oscillation being a common issue. Not saying that's he case with this circuit, no idea. If you haven't already, I'd poke around FSB and the like and make sure there are more fully functioning builds documented than not.
Click to expand...
I used a few of his schematics to build pedal. Always nice but this one is different. The most current version is it, he didn't have issues with it.
jwin615 said:
Or the NJM2777which requires very little external circuitry and runs happily at 9v
Click to expand...
It depends on if you are able to get your hands on it :-)
 
What do you print the top label on?

Unrelated hint: OPA2196 and OPA2990 are good options for guitar/bass headphone amps, especially if battery powered (super low idle current), as long as you use a series resistor on the output. Something like 20 ohms or more.
 
Color labels are vinyl sticker sheets for my laser printer. Transparent labels are transparent sticker sheets.
Even though both say "waterproof" etc I always put a transparent sticker sheet on top.
Still have to tinker with the color saturation. Sometimes it's to pale sometimes to dark...
 
It‘s done!
Had to go to reddit for Karma farming and try to fish for compliments :ROFLMAO:

IMG_1082.jpeg IMG_1067.jpeg IMG_1094.jpeg

This time everything is on a separate pcb and in a big 1590X enclosure. Baja Reactor, Unicab and the TPA module each fit in a 125B. The headphone amp should fit perfectly in an 1590A. I used Kicad to create the layout of the Reactor and the headphone amp and ordered them from JLCPCB.
The headphone amp is great on a cab too, but more is more. Even if I run the TPA3118 on 9V it's fine for home use.
For the HP Out and AUX In I used shielded wire because the signal is pretty strong in this pedal. The audio probe picks up the signal pretty loud when I hold it 1cm above the pcbs.
Everything is on all the time, no switches no LEDs.

Possible changes:
- add a regulator and power the pedal with 24 to have a louder TPA module
- there is still some empty space in the middle between the Reactor and Unicab where I could add two 3PDT toggle switches but currently it's fine the way it is.
- add another jack to bypass the amps to hook it up to another amp.

Lesson learned:
- 3.5mm jacks are not designed for thick 1590X walls, I had to glue them in place. On the picture the nuts are missing but I will add them again also with glue for stability (one fell behind my cab before I glued them in place...)
- PCB layouts are sometimes important! :-)
- when you buy a ready to use TPA module check for the dimensions. I have a larger one I ordered a long time ago which I finally wanted to use but it is too large (with heatsink, large caps and a fixed pot)
- the wiring could be nicer
- at first I thought I messed up the Reactor pcb again but it turned out that loud input was the problem. Seems to be sensitive.

Still not learned:
- if I need the large cap for the TPA module, currently it's a 1000uF instead of a 4700uF mentioned elsewhere because I just don't have a larger one.
- how to drill correctly
- electronics
 
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